The Applicant has developed a range of Memjet® inkjet printers as described in, for example, WO2011/143700, WO2011/143699 and WO2009/089567, the contents of which are herein incorporated by reference. Memjet® printers employ a stationary pagewidth printhead in combination with a feed mechanism which feeds print media past the printhead in a single pass. Memjet® printers therefore provide much higher printing speeds than conventional scanning inkjet printers.
An inkjet printhead is comprised of a plurality (typically thousands) of individual inkjet nozzle devices, each supplied with ink. Each inkjet nozzle device typically comprises a firing chamber having a nozzle aperture and an actuator for ejecting ink through the nozzle aperture. The design space for inkjet nozzle devices is vast and a plethora of different nozzle devices have been described in the patent literature, including different types of actuators and different device configurations.
One of the most important criteria in designing an inkjet nozzle device is achieving ink drop trajectories perpendicular to the nozzle plane. If each drop is ejected perpendicularly outward, the tail following the drop will not catch and deposit on the nozzle edge; a source of flooding and drop misdirection is thus avoided. Additionally, with perpendicular trajectories, the primary satellite formed by breakup of the droplet tail can be made to land on top of the main drop on the page, hiding that satellite. Significant improvements in print quality can therefore be obtained with perpendicular drop trajectories.
However, inkjet nozzle devices usually have an inherent degree of asymmetry, which means that ink droplets may be ejected somewhat skewed from the nozzle plate of the printhead. With skewed droplet ejection, satellite droplets tend to land on print media at a different position than the main droplet and this causes a reduction in print quality.
Hitherto, most attempts to minimize the effects of satellites have focused on compensating for asymmetry in the nozzle device. For example, U.S. Pat. No. 7,780,271 (assigned to Zamtec Ltd) describes an inkjet nozzle device having a heating element which is offset from the nozzle aperture. The offset compensates for asymmetric bubble formation in the firing chamber and enables non-skewed droplet ejection.
U.S. Pat. No. 5,666,143 (assigned to Hewlett-Packard Company) describes inkjet nozzle devices having multiple chamber inlets. Each nozzle chamber has a pair of side inlets and each nozzle chamber is asymmetric.
U.S. Pat. No. 7,841,697 (assigned to Zamtec Ltd) describes inkjet nozzle devices having multiple chamber inlets. Each nozzle chamber has one inlet defined in a sidewall and one inlet defined in floor of the nozzle chamber.
It would be desirable to provide an inkjet nozzle device, which minimizes satellite droplet formation and improves print quality. It would be further desirable to provide an inkjet nozzle device with improved ink flow into nozzle chambers and greater tolerance to blockages in chamber inlets.